1. Field of the Invention
The present invention relates to a scintillation camera for radiographing the two-dimensional distribution image or tomographic image in accordance with radioactive isotope distributed in an examined body, and more particularly, relates to a scintillation camera including a carrier for exchanging collimators attached to detectors.
2. Description of the Related Art
In the case of the detector attached to the scintillation camera, gamma rays radiated from the examined body interact in the scintillator, and fluorescent rays proportional to their absorption energy are emitted from the scintillator. The fluorescent rays are received by the photomultiplier tube and electric pulses proportional to the amount of fluorescent rays are output. The pulses output are signal-processed to form the two-dimensional distribution image or tomographic image.
The detector includes a collimator opposed to the examined body and located in front of the scintillator. The collimator is a plate made of lead and formed with a plurality of holes. The collimator serves to introduce those gamma rays, which are radially radiated from the examined body and which are parallel to its holes, to the scintillator, while the collimator serves to shield the other gamma rays which are radiated obliquely to the collimator's holes. The collimators are grouped to use for high, medium and low energies, depending upon the energies of radioactive isotope. They are also grouped according to sizes of their holes, because resolution and sensitivity of images change depending upon the sizes of their holes. Therefore, various kinds of collimators are available and they must be selected to meet the purposes of radiographing. In other words, they must be changed every time when radiographing purposes change.
Conventionally, one scintillation camera usually includes one detector and one collimator. Only one collimator is exchanged with another, every time radiographing purposes change, so that the exchanging operation is carried out by hands or by a carrier and is quite easy.
However, scintillation cameras have recently been developed which have high qualities, one type of which has plural (more concretely, three or four) detectors. Since one detector needs to have one collimator, plural collimators must be attached to one scintillation camera. When radiographing purposes change, therefore, plural collimators must be exchanged with other ones. When the collimators are exchanged with other ones one by one by hand or by the carrier, as usually seen in the conventional cases, quite a long period of time is required and the efficiency of exchanging operation is quite low.